The small building on which the sign is placed had a dual function.
It was a position well-placed to monitor the fire north of Fort input and the bastion of the tank. But it also housed the latrines, ease of places of the garrison.
It then had a roof and a door. One can observe the long discharge pipe plunging into the valley: amazing all at the time drain!
There remains no trace of the body guard who was attached to the back of the "Grand'Tour" or the door that was in the seventeenth century the main entrance of the citadel.

Observe now the tower wall.
You can guess, to the left of the current door (opened under Louis XVIII), the medieval entrance which can still observe the arch.
It opened originally nearly two meters above the ground.
Suggestion of the route of the medieval gate